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Soil Suitability/ Nitrate Loading Study Irerracon <br />Thornton Road Trailer Parking Facility ■ Lodi, California <br />December 15, 2021 ■ Terracon Project No. NA217079 <br />A discussion of regional groundwater, including depth to groundwater and seasonal trends are <br />included in Section 1.4.1. <br />2.2.2 Potential Ground Water Contamination Issues <br />A discussion of issues related to potential groundwater contamination is included in Section 1.4.2. <br />2.2.3 Current and Future On -Site Ground Water Uses <br />The proposed building is proposed to be connected to the municipal groundwater supply well. <br />2.3 Sources and Impact of Nitrate to Groundwater <br />2.3.1 Current Off -Site Sources of Nitrate <br />Agricultural land use in the area may be the most significant sources of nitrate in groundwater. <br />Septic tank use in the vicinity is discussed in Section 1.3.5. <br />2.3.2 Contribution of Rainfall <br />An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. <br />Average precipitation and potential evapotranspiration (ETo) data was obtained from the <br />California Irrigation Management Information System (CIMIS) from the Lodi Station (042) and <br />Lodi West (166). The estimate first determines whetherthe average monthly precipitation exceeds <br />average monthly evapotranspiration (ET). If so, then the difference is potential rainfall recharge. <br />Due to the relatively flat nature of the site and proposed stormwater retention basins, runoff should <br />be minimal. In February 2020, the EHD approved an adjustment to the evapotranspiration (ET) <br />rate based on net rainfall recharge calculation utilizing University of California (UC) plant factors <br />(PF) for established landscape plants. Terracon calculated the ET adjustment factor (actual ET) <br />based on the proposed commercial landscape. Refer to Appendix F Water Balance Recharge <br />Analysis for monthly precipitation and ET averages. <br />Table 7. <br />Net Rainfall Recharge <br />Based on this method, the average net rainfall recharge for the site is estimated to be 11.46 <br />inches/year. <br />Responsive ■ Resourceful ■ Reliable 13 <br />ET <br />Net Rainfall <br />CIMIS Station <br />Average Precipitation <br />Potential ETO <br />Actual ET <br />Adjustment <br />Recharge <br />Number/ Location <br />(in/year) <br />(in/year) <br />Factor <br />(in/month) <br />(in/year) <br />042/Lodi <br />15.46 <br />50.50 <br />0.21 <br />9.09 <br />11.46 <br />166/Lodi West <br />Based on this method, the average net rainfall recharge for the site is estimated to be 11.46 <br />inches/year. <br />Responsive ■ Resourceful ■ Reliable 13 <br />